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6CY7 Stereo Amp
http://www.diyaudioprojects.com/Forum/viewtopic.php?f=9&t=5222
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Author:  slack73 [ 25 Jun 2018, 04:42 ]
Post subject:  Re: 6CY7 Stereo Amp

Suncalc wrote:

I hope this helps.


Very much so. Thanks for taking the time to explain all that.

Suncalc wrote:

It was only after thinking about it for a while that I realized that a simple 3dB difference in speaker sensitivity meant the spearers only sound half as loud. By the time you get to a 6dB difference it's really shocking how little sound comes out of an insensitive speaker. This is one of the reasons that today, most people recommend simple high sensitivity drivers (mid 90dB range) for these small SETs. I routinely use small 2-way bookshelf speakers with sensitivity of about 90dB with this amp for casual listening.


Until I built the 4S and the Lacewood, my tube "experience" (or lack thereof) was mainly cobbling together low-wattage guitar amps. Some years back I had built a Fender Princeton style circuit in a head for a friend to use in his studio. I think it ended up in the 4 to 7 watt range. I remember how shocked we were at how loud it was hooked up to a 4x12 Marshall cabinet loaded with Celestion Vintage 30's. I just looked up the specs on the Celestions, and they are advertised at 100db sensitivity. This explains a lot.

Anyhow, now I have a great excuse to build another set of speakers. :up:

Thanks again Matt

Author:  Suncalc [ 17 Mar 2019, 18:08 ]
Post subject:  Re: 6CY7 Stereo Amp

Bass Response!

I am sitting in my office and working on my 6L6 SE-UL analysis write up and listening to this fine little amplifier.

Well, on the play list comes up Stevie Ray Vaughan and Albert King collaborating on a great rendition of "Pride and Joy" off of the album "In Session". I defy anyone to listen to this track, through this amp with some well match speakers and then claim that there is insufficient bass.

I've got both well controlled thumping bass and super clean blues guitar riffs. This album should put a smile on your face!

Author:  tapehissmakesmehappy [ 03 Jun 2019, 14:53 ]
Post subject:  Re: 6CY7 Stereo Amp

Hey Matt,
I was wondering did you ever get around to making a 6CY7 2.0 or monoblock (maybe with higher output, fingers crossed)? I wanted to pair the amp with Frugal Horns but I wanted to check with you before ordering parts incase you had better plans in the works. Also it would be really fantastic if you could take the pictures of the 6CY7 build and label grounding and wires like you did on the 4S preamp. This would be my first build and while I understand the schematic and have read over everything a few times I want to have a solid grasp on things before I order parts.

Author:  okisoki [ 31 Dec 2019, 13:36 ]
Post subject:  Re: 6CY7 Stereo Amp

Hola buenas.
Alguien me podría indicar cómo conseguir la válvula 6CY7.

Gracias por la ayuda, resido en España.

Author:  nodz [ 17 Jan 2020, 03:03 ]
Post subject:  Re: 6CY7 Stereo Amp

Just getting back to valve theory after 10 years in the wilderness and trying to figure out the load lines for this as per the article on the tube projects page for this amp. For the life of me I can't work out how to get 300V, 6mA and 47V, 58mA with the 5K OP transformer. The reason I ask was because I was thinking of applying theory to 6CM7 valve, which has similar characteristics to this but using 4K OP transformer rather than the 5K. Could anyone please point me in the right direction?

Author:  Suncalc [ 18 Jan 2020, 16:39 ]
Post subject:  Re: 6CY7 Stereo Amp

nodz wrote:
For the life of me I can't work out how to get 300V, 6mA and 47V, 58mA with the 5K OP transformer.
I think you are being confused by the load line. When you look at the load line for the power stage, this is the AC load line and not the DC load line. With the power stage bias set at set at Vp=188v and Ip=29mA, the points on the load line you reference are the result of a full +/- 29v peak (20.5v rms) drive and the resultant voltage swing in the load. The slope of the AC load line is due to the value of the output transformer impedance (i.e. 5kΩ).

Does this help?

Author:  nodz [ 23 Jan 2020, 15:36 ]
Post subject:  Re: 6CY7 Stereo Amp

@Suncalc, thanks - refreshing my memory here. Managed to do the calcs using 4K load. Using Rk as 680ohm got Vg = -23.7V, Vp=164V, Ip=34mA, P=1.7W (Va=24.8V, Ia=62mA, Ve=258V, Ie=10mA) D=3.8%, Ds=2.2%/W, Rp at 885Ohm B+=218V (164+23.7+0.034*885). Phew! So using same PS and 680ohm cathode resistor and 4K load shouldn't get too dissimilar results from original

Author:  Suncalc [ 01 Mar 2020, 19:55 ]
Post subject:  Re: 6CY7 Stereo Amp

Another fine example of how this amp sounds;

Bachman-Turner Overdrive, "Takin' Care of Business". Bass is deep and strong, guitar riffs are clean and fast, symbols pop to the surface. "Blue Moanin'" is also excellent!

This amp rocks! 8-)

Author:  Suncalc [ 01 Mar 2020, 20:03 ]
Post subject:  Re: 6CY7 Stereo Amp

Also, for anyone that wants a good demonstration of how fast is this amp, try "Highway Star" off the Deep Purple "Machine Head" disc 2 (Roger Glover Remixes). Especially the beginning as the guitar riffs build up, listen for the finger movement on the strings and notice how fast the snare hits pop out of the background.

I am always amazed at how truly excellent such a simple amp can sound!

Author:  Woodo [ 02 Mar 2020, 15:05 ]
Post subject:  Re: 6CY7 Stereo Amp

Matt, I don’t have your 6cy7 design, so the 300b will have to do. i look forward to playing those tracks on it to see how it performs. Those tracks take me back a while.

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